As the airport is located west of London and as its runways run east–west, an airliner's landing approach is usually directly over the conurbation of London when the wind is from the west, which is most of the time.

Heathrow Airport originated in 1929 as a small airfield (Great West Aerodrome) on land south-east of the hamlet of Heathrow from which the airport takes its name. At that time there were farms, market gardens and orchards there: there was a "Heathrow Farm" about where the old Terminal 1 was and where Terminal 2 is, a "Heathrow Hall" and a "Heathrow House". This hamlet was largely along a country lane (Heathrow Road) which ran roughly along the east and south edges of the present central terminals area.

Development of the whole Heathrow area as a very much larger airport began in 1944: it was stated to be for long-distance military aircraft bound for the Far East. But by the time the airfield was nearing completion, World War II had ended. The government continued to develop the airport as a civil airport. The airport was opened on 25 March 1946 as London Airport and was renamed Heathrow Airport in 1966. The masterplan[clarification needed] for the airport was designed by Sir Frederick Gibberd, who designed the original terminals and central area buildings, including the original control tower and the multi-faith chapel of St George's.

Heathrow Airport is used by over 80 airlines flying to 185 destinations in 84 countries. The airport is the primary hub of British Airways and is a base for Virgin Atlantic. It has four passenger terminals (numbered 2 to 5) and a cargo terminal. Of Heathrow's 78 million passengers in 2017, 94% were international travellers; the remaining 6% were bound for (or arriving from) places in the UK.[8] The busiest single destination in passenger numbers is New York, with over 3 million passengers flying between Heathrow and JFK Airport in 2013.[9]

In the 1950s, Heathrow had six runways, arranged in three pairs at different angles in the shape of a hexagram with the permanent passenger terminal in the middle and the older terminal along the north edge of the field; two of its runways would always be within 30° of the wind direction. As the required length for runways has grown, Heathrow now has only two parallel runways running east–west. These are extended versions of the two east–west runways from the original hexagram. From the air, almost all of the original runways can still be seen, incorporated into the present system of taxiways. North of the northern runway and the former taxiway and aprons, now the site of extensive car parks, is the entrance to the access tunnel and the site of Heathrow's unofficial "gate guardian". For many years the home of a 40% scale model of a British Airways Concorde, G-CONC, the site has been occupied by a model of an Emirates Airbus A380 since 2008.[10]

The airport has its own resident press corps, consisting of six photographers and one TV crew, serving all the major newspapers and television stations around the world.[12]

Most of Heathrow's internal roads are initial letter coded by area: N in the north (e.g. Newall Road), E in the east (e.g. Elmdon Road), S in the south (e.g. Stratford Road), W in the west (e.g. Walrus Road), C in the centre (e.g. Camborne Road).

Air traffic controllers at Heathrow Approach Control (based in Swanwick, Hampshire) then guide the aircraft to their final approach, merging aircraft from the four holds into a single stream of traffic, sometimes as close as 2.5 nautical miles (4.6 km; 2.9 mi) apart. Considerable use is made of continuous descent approach techniques to minimize the environmental effects of incoming aircraft, particularly at night.[13] Once an aircraft is established on its final approach, control is handed over to Heathrow Tower.

When runway alternation was introduced, aircraft generated significantly more noise on departure than when landing, so a preference for westerly operations during daylight was introduced, which continues to this day.[14] In this mode, aircraft depart towards the west and approach from the east over London, thereby minimizing the impact of noise on the most densely populated areas. Heathrow's two runways generally operate in segregated mode, whereby arriving aircraft are allocated to one runway and departing aircraft to the other. To further reduce noise nuisance to people beneath the approach and departure routes, the use of runways 27R and 27L is swapped at 15:00 each day if the wind is from the west. When landings are easterly there is no alternation; 09L remains the landing runway and 09R the departure runway due to the legacy of the now rescinded Cranford Agreement, pending taxiway works to allow the roles to be reversed. Occasionally, landings are allowed on the nominated departure runway, to help reduce airborne delays and to position landing aircraft closer to their terminal, reducing taxi times.

Night-time flights at Heathrow are subject to restrictions. Between 23:00 and 04:00, the noisiest aircraft (rated QC/8 and QC/16) cannot be scheduled for operation. In addition, during the night quota period (23:30–06:00) there are four limits:

A limit on the number of flights allowed;

A Quota Count system which limits the total amount of noise permitted, but allows operators to choose to operate fewer noisy aircraft or a greater number of quieter planes;[15]

QC/4 aircraft cannot be scheduled for operation.

A voluntary agreement with the airlines that no early morning arrivals will be scheduled to land before 04:30.

A trial of "noise relief zones" ran from December 2012 to March 2013, which concentrated approach flight paths into defined areas compared with the existing paths which were spread out. The zones used alternated weekly, meaning residents in the "no-fly" areas received respite from aircraft noise for set periods.[16] However, it was concluded that some residents in other areas experienced a significant disbenefit as a result of the trial and that it should therefore not be taken forward in its current form. Heathrow received more than 25,000 noise complaints in just three months over the summer of 2016, but around half were made by the same ten people.[17]

Until it was required to sell Gatwick and Stansted Airports, Heathrow Airport Holdings held a dominant position in the London aviation market, and has been heavily regulated by the Civil Aviation Authority (CAA) as to how much it can charge airlines to land. The annual increase in landing charge per passenger was capped at inflation minus 3% until 1 April 2003. From 2003 to 2007 charges increased by inflation plus 6.5% per year, taking the fee to £9.28 per passenger in 2007. In March 2008, the CAA announced that the charge would be allowed to increase by 23.5% to £12.80 from 1 April 2008 and by inflation plus 7.5% for each of the following four years.[18] In April 2013, the CAA announced a proposal for Heathrow to charge fees calculated by inflation minus 1.3%, continuing until 2019.[19] Whilst the cost of landing at Heathrow is determined by the CAA and Heathrow Airport Holdings, the allocation of landing slots to airlines is carried out by Airport Co-ordination Limited (ACL).[20]

Until 2008, air traffic between Heathrow and the United States was strictly governed by the countries' bilateral Bermuda II treaty. The treaty originally allowed only British Airways, Pan Am and TWA to fly from Heathrow to the US. In 1991, PAA and TWA sold their rights to United Airlines and American Airlines respectively, while Virgin Atlantic was added to the list of airlines allowed to operate on these routes. The Bermuda bilateral agreement conflicted with the Right of Establishment of the United Kingdom in relation to its EU membership, and as a consequence the UK was ordered to drop the agreement in 2004. A new "open skies" agreement was signed by the United States and the European Union on 30 April 2007 and came into effect on 30 March 2008. Shortly afterwards, additional US airlines, including Northwest Airlines, Continental Airlines, US Airways and Delta Air Lines started services to Heathrow.

The airport has been criticised in recent years for overcrowding and delays;[21] according to Heathrow Airport Holdings, Heathrow's facilities were originally designed to accommodate 55 million passengers annually. The number of passengers using the airport reached a record 70 million in 2012.[22] In 2007 the airport was voted the world's least favourite, alongside Chicago O'Hare, in a TripAdvisor survey.[23] However, the opening of Terminal 5 in 2008 has relieved some pressure on terminal facilities, increasing the airport's terminal capacity to 90 million passengers per year. A tie-up is also in place with McLaren Applied Technologies to optimize the general procedure, reducing delays and pollution.[24]

With only two runways, operating at over 98% of their capacity, Heathrow has little room for more flights, although the increasing use of larger aircraft such as the Airbus A380 will allow some increase in passenger numbers. It is difficult for existing airlines to obtain landing slots to enable them to increase their services from the airport, or for new airlines to start operations.[25] To increase the number of flights, Heathrow Airport Holdings has proposed using the existing two runways in 'mixed mode' whereby aircraft would be allowed to take off and land on the same runway. This would increase the airport's capacity from its current 480,000 movements per year to as many as 550,000 according to British Airways CEO Willie Walsh.[26] Heathrow Airport Holdings has also proposed building a third runway to the north of the airport, which would significantly increase traffic capacity (see Future expansion below).[27]

Full body scanners are now used at the airport, and passengers who object to their use after being selected are required to submit to a hand search in a private room.[28] The scanners display passengers' bodies as a cartoon-style figure, with indicators showing where concealed items may be.[28] The new imagery was introduced initially as a trial in September 2011 following complaints over privacy.[29]

The airport's newest terminal, officially known as the Queen's Terminal, was opened on 4 June 2014.[30][31] Designed by Spanish architect Luis Vidal, it was built on the site that had been occupied by the original Terminal 2 and the Queens Building.[32][33] The main complex was completed in November 2013 and underwent six months of testing before opening to passengers. It includes a satellite pier (T2B), a 1,340-space car park, an energy center[clarification needed] and a cooling station to generate chilled water. There are 52 shops and 17 bars and restaurants.[34]

The original Terminal 2 opened as the Europa Building in 1955 and was the airport's oldest terminal. It had an area of 49,654 m2 (534,470 sq ft) and was designed to handle around 1.2 million passengers annually. In its final years it accommodated up to 8 million. A total of 316 million passengers passed through the terminal in its lifetime. The building was demolished in 2010, along with the Queens Building which had housed airline company offices.[37]

Terminal 3 opened as the Oceanic Terminal on 13 November 1961 to handle flight departures for long-haul routes for foreign carriers to the United States, Asia and other Far Eastern destinations.[38] At this time the airport had a direct helicopter service to Central London from the gardens on the roof of the terminal building. Renamed Terminal 3 in 1968, it was expanded in 1970 with the addition of an arrivals building. Other facilities added included the UK's first moving walkways. In 2006, the new £105 million Pier 6 was completed[39] to accommodate the Airbus A380 superjumbo; Emirates and Qantas operate regular flights from Terminal 3 using the Airbus A380.

Redevelopment of Terminal 3's forecourt by the addition of a new four-lane drop-off area and a large pedestrianised plaza, complete with canopy to the front of the terminal building, was completed in 2007. These improvements were intended to improve passengers' experience, reduce traffic congestion and improve security.[40] As part of this project, Virgin Atlantic was assigned its own dedicated check-in area, known as 'Zone A', which features a large sculpture and atrium.

Opened in 1986, Terminal 4 is situated to the south of the southern runway next to the cargo terminal and is connected to Terminals 2 and 3 by the Heathrow Cargo Tunnel. The terminal has an area of 105,481 m2 (1,135,390 sq ft) and is now home to the SkyTeam alliance, with the exception of Delta Air Lines and Middle East Airlines, which use Terminal 3, Oneworld carriers Malaysia Airlines and Qatar Airways, and to most unaffiliated carriers. It has undergone a £200m upgrade to enable it to accommodate 45 airlines with an upgraded forecourt to reduce traffic congestion and improve security. Most flights that go to Terminal 4 are flights coming from Asia and North Africa, as well as a few flights to Europe. An extended check-in area with renovated piers and departure lounges and a new baggage system were installed, and two new stands were built to accommodate the Airbus A380; Etihad Airways, Korean Air, Malaysia Airlines and Qatar Airways operate regular A380 flights.[42]EL AL operates some regular Boeing 747 flights.

Terminal 5 lies between the northern and southern runways at the western end of the Heathrow site and was opened by Queen Elizabeth II on 14 March 2008,[43] some 19 years after its inception. It opened to the public on 27 March 2008, and British Airways and its partner company Iberia have exclusive use of this terminal. The first passenger to enter Terminal 5 was a UK ex-pat from Kenya who passed through security at 04:30 on the day. He was presented with a boarding pass by the British Airways CEO Willie Walsh for the first departing flight, BA302 to Paris. During the two weeks after its opening, operations were disrupted by problems with the terminal's IT systems, coupled with insufficient testing and staff training, which caused over 500 flights to be cancelled.[44] Until March 2012, Terminal 5 was exclusively used by British Airways as its global hub; however, because of the merger, on 25 March Iberia's operations at Heathrow were moved to the terminal, making it the home of International Airlines Group.[45]

Built at a cost of £4.3 billion, the terminal consists of a four-story main terminal building (Concourse A) and two satellite buildings linked to the main terminal by an underground people mover transit system. The second satellite (Concourse C), includes dedicated aircraft stands for the Airbus A380. It became fully operational on 1 June 2011. Terminal 5 was voted Skytrax World's Best Airport Terminal 2014 in the Annual World Airport Awards.[46]

The main terminal building (Concourse A) has an area of 300,000 square metres (3,200,000 sq ft) while Concourse B covers 60,000 square metres (650,000 sq ft).[47] It has 60 aircraft stands and capacity for 30 million passengers annually as well as more than 100 shops and restaurants.[48] It is also home to British Airways’ Flagship lounge, the Concorde Room, alongside four further British Airways branded lounges.[49]

A further building, designated Concourse D and of similar size to Concourse C, may yet be built to the east of the existing site, providing up to another 16 stands. Following British Airways' merger with Iberia, this may become a priority since the combined business will require accommodation at Heathrow under one roof to maximise the cost savings envisaged under the deal. A proposal for Concourse D featured in Heathrow's most recent capital investment plan.

The transport network around the airport has been extended to cope with the increase in passenger numbers. A dedicated motorway spur links the terminal to the M25 (between junctions 14 and 15). The terminal has a 3,800 space multi-story car park. A more distant long-stay car park for business passengers is connected to the terminal by a personal rapid transit system, which became operational in the spring of 2011.[50] New branches of both the Heathrow Express and the Underground's Piccadilly line serve a new shared Heathrow Terminal 5 station.

British Airways (most destinations, except those at Terminal 3) and Iberia

Following the opening of Terminal 5 in March 2008, a complex programme of terminal moves was implemented. This saw many airlines move so as to be grouped in terminals by airline alliance as far as possible.[52]

Following the opening of Phase 1 of the new Terminal 2 in June 2014, all Star Alliance member airlines[53] (with the exception of new member Air India which moved in early 2017) along with Aer Lingus and Germanwings relocated to Terminal 2 in a phased process completed on 22 October 2014. Additionally, by 30 June 2015 all airlines left Terminal 1 in preparation for its demolition to make room for the construction of Phase 2 of Terminal 2.[54] Some other airlines made further minor moves at a later point, e.g. Air India moving from Terminal 4 to the other Star Alliance carriers in Terminal 2[55] or Delta Air Lines merging all departures in Terminal 3 instead of a split between Terminals 3 and 4.[56]

Terminal 1 opened in 1968 and was inaugurated by Queen Elizabeth II in April 1969.[57][58] Before Terminal 5 opened, Terminal 1 was the Heathrow base for British Airways' (BA) domestic and European network and for a few of its long haul routes. The acquisition of British Midland International (BMI) in 2012 by BA's owner International Airlines Group meant British Airways took over BMI's short-haul and medium-haul destinations from the terminal.[59] Terminal 1 was also the main base for most Star Alliance members, some Star Alliance members were also based at Terminal 3.

Terminal 1 closed at the end of June 2015. Its site is being used for an extension to Terminal 2,[60] which opened in June 2014. A number of newer boarding gates used by Terminal 1 had been built as part of the Terminal 2 development and are being retained as part of Terminal 2.[61][62] The last tenants along with British Airways were El Al, Icelandair, the one who moved to Terminal 2 on 25 March 2015, and LATAM Brasil, the third one to move in to Terminal 3 on 27 May, 2015. British Airways was the last operator in Terminal 1. Two flights of this carrier, one departing to Hanover and one arriving from Baku, marked the terminal closure on 29 June 2015. British Airways operations have been relocated to Terminals 3 and 5.[63]

At one time the British Airways head office was located within Heathrow Airport at Speedbird House[102] before the completion of Waterside, the current BA head office in Harmondsworth, in June 1998.[103]

To the north of the airfield lies the Northern Perimeter Road, along which most of Heathrow's car rental agencies are based, and Bath Road, which runs parallel to it, but outside the airport campus. This is nicknamed "The Strip" by locals, because of its continuous line of airport hotels.

All terminals lie within the Heathrow Free Travel Zone with free travel between the terminals. Terminals 2 and 3 are within walking distance of each other. Transfers from Terminals 2 and 3 to Terminal 4 and 5 are provided by Heathrow Express trains and the London UndergroundPiccadilly line.[106] Direct transfer between Terminals 4 and 5 is provided by London Buses routes 482 and 490.[107]

ULTra Personal Rapid Transport opened in April 2011 to shuttle passengers between Terminal 5 and the business car park at a speed of up to 40 km/h (25 mph). There are 21 small transportation pods that can each carry up to four adults, two children, and their luggage. The pods are battery-powered and run on a four-kilometre track. The capsules run on demand. The provider claims a 95% availability rate and no accidents so far.[108] Plans to use the same technology to connect Terminals 2 and 3 to remote car parks were included in the draft 2014–2019 five-year master plan but have since been deferred due to other priorities.[109]

Entrance at the southern end of the M4 Motorway spur, showing a scale model of Concorde, replaced since 2008 by the Emirates A380 scale model.[112]

Heathrow is accessible via the nearby M4 motorway or A4 road (Terminals 2–3), the M25 motorway (Terminals 4 and 5) and the A30 road (Terminal 4). There are drop-off and pick-up areas at all terminals and short-[113][114] and long-stay[115] multi-storey car parks. All the Heathrow forecourts are drop-off only.[116] There are further car parks, not run by Heathrow Airport Holdings, just outside the airport: the most recognisable is the National Car Parks facility, although there are many other options; these car parks are connected to the terminals by shuttle buses.

Four parallel tunnels under the northern runway connect the M4 Heathrow spur and the A4 road to Terminals 2–3. The two larger tunnels are each two lanes wide and are used for motorised traffic. The two smaller tunnels were originally reserved for pedestrians and bicycles; to increase traffic capacity the cycle lanes have been modified to each take a single lane of cars, although bicycles still have priority over cars. Pedestrian access to the smaller tunnels has been discontinued, with the free bus services being used instead.

There are (mainly off-road) bicycle routes to some of the terminals.[117] Free bicycle parking places are available in car parks 1 and 1A, at Terminal 4, and to the North and South of Terminal 5's Interchange Plaza. Travelers are not allowed to cycle through the main tunnel to access Terminals 2 and 3 (Terminal 1 closed in 2015).[118]

On 3 March 1948, Sabena Douglas DC3 OO-AWH crashed in fog. Three crew and 19 of the 22 passengers on board died.[119]

On 31 October 1950, BEAVickers Viking G-AHPN crashed at Heathrow after hitting the runway during a go-around. Three crew and 25 passengers died.[120]

On 16 January 1955, BEAVickers Viscount G-AMOK crashed into barriers whilst taking off in fog from a disused runway strip parallel to the desired runway. There were 2 injuries.[121]

On 22 June 1955, BOACde Havilland Dove G-ALTM crashed just short of the runway during a filming flight, when the pilot shut-down the incorrect engine. There were no casualties.[122]

On 1 October 1956, XA897, an Avro Vulcan strategic bomber of the Royal Air Force, crashed at Heathrow after an approach in bad weather. The Vulcan was the first to be delivered to the RAF, and was returning from a demonstration flight to Australia and New Zealand. The pilot and co-pilot ejected and survived, but the four other occupants were killed.[123]

On 7 January 1960, Vickers Viscount G-AOHU of BEA was damaged beyond economic repair when the nose wheel collapsed on landing. A fire then developed and burnt out the fuselage. There were no casualties among the 59 people on board.[124]

On 27 October 1965, BEA Vickers Vanguard G-APEE, flying from Edinburgh, crashed on Runway 28R while attempting to land in poor visibility. All 30 passengers and six crew on board died.[125][126]

On 8 April 1968, BOAC Flight 712Boeing 707 G-ARWE, departing for Australia via Singapore, suffered an engine fire just after take-off. The engine fell from the wing into a nearby gravel pit in Staines, before the plane managed to perform an emergency landing with the wing on fire. However, the plane was consumed by fire once on the ground. Five people – four passengers and a flight attendant – died, while 122 survived. The flight attendant, Barbara Harrison, who helped with the evacuation, was posthumously awarded the George Cross.[127]

On 3 July 1968, the port flap operating rod of G-AMAD, an Airspeed Ambassador operated by BKS Air Transport failed due to fatigue, thereby allowing the port flaps to retract. This resulted in a rolling movement to port which could not be controlled during the approach, causing the aircraft to contact the grass and swerve towards the terminal building. It hit two parked British European Airways Hawker Siddeley Trident aircraft, burst into flames and came to rest against the ground floor of the terminal building. Six of the eight crew died, as did eight horses on board. Trident G-ARPT was written off,[128] and Trident G-ARPI was badly damaged, but subsequently repaired, only to be lost in the Staines crash in 1972.

On 18 June 1972, Trident G-ARPI, operating as BEA548, crashed in a field close to the Crooked Billet Public House, Staines, two minutes after taking off. All 118 passengers and crew on board died.[129]

On 17 January 2008, a British Airways Boeing 777-236ER, G-YMMM, operating flight BA038 from Beijing, crash-landed at Heathrow. The aircraft landed on grass short of the south runway, then slid to the edge of the runway and stopped on the threshold, leading to 18 minor injuries. The aircraft was later found to have suffered loss of thrust caused by fuel icing.[130]

On 8 June 1968, James Earl Ray, the man convicted of 4 April 1968 assassination of Martin Luther King, Jr., was captured and arrested at Heathrow Airport while attempting to leave the United Kingdom on a false Canadian passport.[131]

On 6 September 1970, El Al Flight 219 experienced an attempted hijack by two PFLP members. One hijacker was killed and the other was subdued as the plane made an emergency landing at Heathrow Airport.

On 19 May 1974, the IRA planted a series of bombs in the Terminal 1 car park. Two people were injured by the explosions.[132]

On 26 November 1983, the Brink's-Mat robbery occurred, in which 6,800 gold bars worth nearly £26 million were taken from a vault near Heathrow. Only a small amount of the gold was recovered, and only two men were convicted of the crime.[133]

On 17 April 1986, semtex explosives were found in the bag of a pregnant Irishwoman attempting to board an El Al flight. The explosives had been given to her by her Jordanian boyfriend and father of her unborn child Nizar Hindawi. The incident became known as the Hindawi Affair.[134]

On 21 December 1988, Pan Am Flight 103 from Heathrow to New York JFK was blown up over Lockerbie, Scotland, killing all 259 on board and 11 other people on the ground. This also still remains the deadliest attack on a US aircraft.[135]

In 1994, over a six-day period, Heathrow was targeted three times (8, 10, and 13 March) by the IRA, which fired 12 mortars. Heathrow was a symbolic target due to its importance to the UK economy, and much disruption was caused when areas of the airport were closed over the period. The gravity of the incident was heightened by the fact that the Queen was being flown back to Heathrow by the RAF on 10 March.[136]

In February 2003, the British Army was deployed to Heathrow along with 1,000 police officers in response to intelligence reports suggesting that al-Qaeda terrorists might launch surface-to-air missile attacks at British or American airliners.[138]

On 17 May 2004, Scotland Yard's Flying Squad foiled an attempt by seven men to steal £40 million in gold bullion and a similar quantity of cash from the Swissport warehouse at Heathrow.[139]

On 25 February 2008, Greenpeace activists protesting against the planned third runway managed to cross the tarmac and climb atop a British Airways Airbus A320, which had just arrived from Manchester Airport. At about 09:45 GMT the protesters unveiled a "Climate Emergency – No Third Runway" banner over the aircraft's tailfin. By 11:00 GMT four arrests had been made.[140]

On 13 March 2008, a man with a rucksack scaled the perimeter fence onto runway 27R, and ran across the grounds, resulting in his subsequent arrest. A controlled explosion of his bag took place, although nothing suspicious was found, and the Metropolitan Police later said that the incident had not been terrorism related.[141]

On 13 July 2015, thirteen activists belonging to the climate change protest group Plane Stupid managed to break through the perimeter fence and get onto the northern runway. They chained themselves together in protest, disrupting hundreds of flights. All were eventually arrested.[142][143]

On 18 December 2010, 'heavy' (9 cm, according to the Heathrow Winter Resilience Enquiry)[144] snowfall caused the closure of the entire airport, causing one of the largest incidents at Heathrow of all time. 4,000 flights were cancelled over five days and 9,500 passengers spent the night at Heathrow on 18 December following the initial snowfall.[145] The problems were caused not only by snow on the runways, but also by snow and ice on the 198 parking stands which were all occupied by aircraft.[146]

There is a long history of expansion proposals for Heathrow since it was first designated as a civil airport. Following the cancellation of the Maplin project in 1974, a fourth terminal was proposed but expansion beyond this ruled out. However, the Airports Inquiries of 1981-83 and the 1985 Airports Policy White Paper considered further expansion and, following a four-year long public inquiry in 1995-99, Terminal 5 was approved. In 2003, after many studies and consultations, the Future of Air Transport White Paper was published which proposed a third runway at Heathrow, as well as a second runway at Stansted Airport.[150] In January 2009, the Transport Secretary at the time, Geoff Hoon announced that the British government supported the expansion of Heathrow by building a third 2,200-metre (7,200 ft) runway and a sixth terminal building.[151] This decision followed the 2003 white paper on the future of air transport in the UK,[152] and a public consultation in November 2007.[153] This was a controversial decision which met with widespread opposition because of the expected greenhouse gas emissions, impact on local communities, as well as noise and air pollution concerns.[154]

Prior to the 2010 general election, the Conservative and Liberal Democrat parties announced that they would prevent the construction of any third runway or further material expansion of the airport's operating capacity. The Mayor of London, then Boris Johnson, took the position that London needs more airport capacity, favouring the construction of an entirely new airport in the Thames Estuary rather than expanding Heathrow.[155] After the Conservative-Liberal Democrat coalition took power, it was announced that the third runway expansion was cancelled.[156] Two years later, leading Conservatives were reported to have changed their minds on the subject.[157]

Another proposal for expanding Heathrow's capacity was the Heathrow Hub, which aims to extend both runways to a total length of about 7,000 metres and divide them into four so that they each provide two, full length runways, allowing simultaneous take-offs and landings while decreasing noise levels.[158][159]

In July 2013, the airport submitted three new proposals for expansion to the Airports Commission, which was established to review airport capacity in the southeast of England. The Airports Commission was chaired by Sir Howard Davies who, at the time of his appointment was in the employ of GIC Private Limited (formerly known as Government Investment Corporation of Singapore) and a member of its International Advisory Board. GIC Private Limited was then (2012), as it remains today, one of Heathrow's principal owners. Sir Howard Davies resigned these positions upon confirmation of his appointment to lead the Airports Commission, although it has been observed that he failed to identify these interests when invited to complete the Airports Commission's register of interests. Each of the three proposals that were to be considered by Sir Howard Davies's commission involved the construction of a third runway, either to the north, northwest or southwest of the airport.[160]

The commission released its interim report in December 2013, shortlisting three options: the north-west third runway option at Heathrow, extending an existing runway at Heathrow, and a second runway at Gatwick Airport. After this report was published, the government confirmed that no options had been ruled out for airport expansion in the South-east and that a new runway would not be built at Heathrow before 2015.[161] The full report was published on 1 July 2015, and backed a third, north-west, runway at Heathrow.[162] Reaction to the report was generally negative, particularly from London Mayor Boris Johnson. One senior Conservative told Channel 4: "Howard Davies has dumped an utter steaming pile of poo on the Prime Minister's desk."[163] On 25 October 2016, the government confirmed that Heathrow would be allowed to build a third runway; however, a final decision would not be taken until winter of 2017/18, after consultations and government votes. The earliest opening year would be 2025. On 5 June 2018, the UK Cabinet approved the third runway, with a full vote planned for Parliament.[164] On 25 June 2018, the House of Commons voted, 415–119, in favour of the third runway.[165] The bill received support from most MPs in the Conservative and Labour parties.[166] A judicial review against the decision is being launched by four London local authorities affected by the expansion—Wandsworth, Richmond, Hillingdon and Hammersmith and Fulham—in partnership with Greenpeace and London mayor Sadiq Khan.[167] Khan previously stated he would take legal action if it were passed by Parliament.[168]

Currently, all rail connections with Heathrow airport run along an east-west alignment to and from central London, and a number of schemes have been proposed over the years to develop new rail transport links with other parts of London and with stations outside the city.[169] This mainline rail service is due to be extended to central London and Essex when the Elizabeth line, currently under construction, opens in 2019.[170]

Among other schemes that have been considered is a rapid transport link between Heathrow and Gatwick Airports, known as Heathwick, which would allow the airports to operate jointly as an airline hub;[176][177] In 2018, the Department for Transport began to invite proposals for privately funded rail links to Heathrow Airport.[178] Projects being considered under this initiative include:

^During periods of westerly operation, aircraft continue to fly in a westerly direction with an easterly tailwind component of up to 5 knots (9.3 km/h; 5.8 mph), if the runway is dry and there is no significant crosswind.